# discretization of Fisher's equation
# with no flux boundary conditions
par h=1
u0'=u0*(1-u0)+(u1-u0)/(h^2)
u[1..39]'=u[j]*(1-u[j]) + (u[j-1]-2*u[j]+u[j+1])/(h^2)
u40'=u40*(1-u40)+(u39-u40)/(h^2)
init u0=.1
@ total=40,dt=.2,meth=qualrk
@ xhi=40,yhi=1,ylo=0,yp=u20
done